JPS61276905A - Production of fine silver particle - Google Patents

Abstract

PURPOSE:To produce fine silver particles having a narrow particle size distribution when the aqueous soln. of an ammoniac silver nitrate complex is reduced with glucose in a hydrophobic reaction vessel to produce fine silver particles, by adding a nonionic surfactant to the reactive soln. CONSTITUTION:The aqueous soln. of glucose as a reducing agent is poured into a reaction vessel after the inside of the vessel is made hydrophobic by oil coating or other method, and a nonionic surfactant such as 'Esomide(R)' or 'Esofat(R)' is added to the soln. and stirred. The aqueous soln. of an ammoniac silver nitrate complex prepd. by adding an aqueous ammonia soln. to an aqueous silver nitrate soln. is slowly added to the soln. in the reaction vessel to reduce the silver nitrate complex with the glucose. Singly dispersed fine silver particles having a narrow particle size distribution are obtd. without causing flocculation.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing fine silver particles.

(Prior art and its problems) Conventionally, as a method for producing fine silver particles, a
Ammoniacal silver nitrate ↑ (1
A method of reducing the container (body) has been used. However,
This method is a great success! This method has the drawback that the particles are attracted to each other and aggregate, resulting in silver particles having only a wide particle size distribution.

(Objective of the Invention) The present invention has been made in order to eliminate the drawbacks listed in -1-, and provides a method for producing fine silver particles with a narrow particle size distribution of bE '0', - 1.

(Means for Solving the Problems) The present invention uses a reducing agent in a hydrophobic reaction tank to produce silver particles by reducing an ammoniacal silver nitrate ↑ (one-body solution). This method is characterized by obtaining 1y-dispersed silver fine particles by adding a surfactant.

The reason why the inner surface of the reaction tank is kept hydrophobic in the production method of the present invention is that in the case of 71 surface water, the precipitation reaction occurs on the wall of the container, so only silver particles with a wide range of agglomerated crystallinity distribution are produced. However, by keeping the inner surface of the reaction tank hydrophobic, the precipitation reaction can occur uniformly in the aqueous solution.

In addition, the reason for adding a cationic surfactant to the reaction solution is that by reducing the ammoniacal silver nitrate ↑ (one-body solution), the silver fine particles precipitated in the aqueous solution do not aggregate and maintain the medium state. It's because of the difference.

In the present invention, methods for keeping the inner surface of the reaction tank hydrophobic include oil coating, surfactant coating, Teflon coating, etc. Nonionic surfactants added to the reaction solution include Esomite, Esof γ So1,
These include Zaflon S-14, 1 Zaflon S-145, etc.

Examples of the present invention will now be described.

(Example 1) 50 g of grape tJIW was added to 300 m of water at 50°C +8
and add the nonionic surfactant Esomy to this solution.
Add 1.2 m (l) of water and stir in a Teflon-coated beaker.
Melt 1.0 g of silver acid at 20 mA in water, add 8 mp of 28% ammonia water to make a solution of 1 g of 8N ammonia nitric acid, and gradually add this to the glucose + esomite solution. The obtained silver particles were thoroughly washed with water and subjected to particle size distribution measurement and electron microscopic observation.

As a result, the average particle size of these silver particles was 1.5 tons! As shown in the figure, the particle size distribution was wide (as shown in the figure), so the shape was approximately fF, and the shape was dispersed.

(Example 2) Grape 1I7i 100, 50'r: water 50
Dissolve 0 ml of this solution and add 0.7 rn of nonionic surfactant +41 agent and -Ri-Freon S-1/II to this solution.
Add ρ and stir in a beaker coated with silicone oil. Also, in a separate beaker, 50 ml of 25 g of silver nitrate was added. of water, add 20ml of 28% ammonia water to the dirt to make an ammoniacal nitric acid solution. Gradually add to 1.
The crushed silver particles are also thoroughly soaked with water by 31' decantation. 1')"L power distribution measurement and electron microscopy/5 mirror observation were performed.

As a result, these fine silver particles had a diameter of 0.9 tt.
m, the particle size distribution was narrow as shown in the figure, and the shape was almost spherical and monodisperse.

(Conventional example) Fight! 70 g of Fi in 400 m4 of water at 50℃?
After 8 hours, stir this solution in a Teflon-coated beaker. In another beaker, add 15g of nitric acid to 30mff of water? Dissolve and add 13 ml of 28% ammonia water to obtain an ammoniacal silver nitrate solution, which is gradually added to the grape IJ,'i solution. The obtained silver particles were thoroughly washed with water by decantation, and subjected to particle size distribution measurement and electron microscopic observation.

As a result, the average particle diameter of the silver particles II was 5.2 μm, and the particle size distribution was agglomerated with a wide range as shown in the figure.

(Effects of the Invention) As is clear from the above explanation, the production method of the present invention is a method for producing silver fine particles by reducing an ammoniacal silver nitrate complex solution using a reducing agent in a hydrophobic reaction tank. , by adding a nonionic surfactant to the reaction solution,
Monodisperse and narrow particle size distribution that cannot be obtained with conventional methods
Since it is possible to produce fine silver particles, it can be said to be a method that can replace conventional production methods.

[Brief explanation of the drawing]

The figure shows the results of measuring the 1'1j degree distribution of each silver i particle using a light transmission type particle size distribution measuring device, with the horizontal axis representing the particle diameter and the 81 minor axis representing the cumulative percentage.

Claims (1)

[Claims] In a method for producing silver fine particles by reducing an ammoniacal silver nitrate complex solution using a reducing agent in a hydrophobic reaction tank, monodispersed silver fine particles are produced by adding a nonionic surfactant to the reaction solution. A method for producing fine silver particles, characterized in that: